The petrified wood

Ocean life is about 2 billion years old, the Alps 100 million, the man just 4 million. Petrified or silicified trees from Arizona or Madagascar date from the Triassic period. They are around 225 million years old.

During the Triassic period, the continent mass is split in two super continents. The Northern part, Laurasia, and the Southern part, Gondwana, then split around a new ocean, the Paleo-Tethys Sea. The climate is warm, the Northern and Southern poles do not exist yet.

Two "salutary" cataclysms

Within a short time, these trees will be exposed to two «Salutary» cataclysms.

It is first a gigantic flood that will uproot from this forest millions of trees. They will be dragged by a powerful river, over a distance of 300kms. During this journey, branches and roots are quite often destroyed. Deposited in lagoons and flood plains, submerged under water, therefore sheltered from the air. In this anaerobic environment the trees will not rot.

At the end of the Tertiary era (Pliocene), a dense tropical forest, made up of Dipterocarpus (of the Magnolia family) and of palm trees, covers the Indonesian volcanic chain from Sumatra in Bali, to the west of Java. From time to time, the volcanoes became active. The force of the eruption was such that surrounding forests were uprooted. A thick layer of burning volcanic ash covered them.

The nearest trees were consumed, those insufficiently covered rotted away. But those between these two extremes benefited from ideal conditions. They became naturally sterilised by the heat which destroyed bacteria normally found in decay.

Pseudomorphosis (by substitution) is the phenomenon by which a mineral presents itself under the appearance of another mineral (the shape of the tree is preserved). The original substance is gradually replaced by a different substance, without chemical reactions: the silica replaces, molecule by molecule, the fibre of the wood, producing the silicified wood, also called petrified wood. The percolation fluids from exposed sediments dissolve the soluble components (calcite, pyrite or silica) drive them from the surface to a certain depth where they are reprecitated.